I have already found a MAJOR glitch. It seems as though when I try to customize the controls, when I start the game I am incapable of turning left, that's a problem. I will not be incapable of enjoying the demo though, I have JoyToKey, so I can easily avert this displeasure, but others may not.
I really enjoyed the demo. The engine controlled very well (although it did slow down for me in a few places like the long hallway before getting the bombs). I didn't really like the fact that bombs were required to enter the second area, and the music for the red area didn't seem to fit that well. But otherwise, this was awesome, and I'm hoping more people discover this. This is the kind of fangame I've always wanted to make myself, simple but well made.
On your comment about the bombs being required to enter the second area - This demo already utilizes tons of backtracking, and to go down there and go after things without the bomb just to find that you need to go back can really ruin the experience for some people.
Yeah, I can understand that you didn't want to confuse players. For me, though, I just knew to backtrack in the direction that led to the bombs before I even went down the elevator. It actually mirrors the NES metroid a lot, except that game didn't restrict access to the fire area. I guess it depends how nonlinear you want to make it, but then again I don't even know if these areas will appear in the final game.